In Long Term Evolution (LTE) systems (3GPP LTE Rel-10), the use of relay nodes has been proposed to improve the coverage and capacity of LTE networks. A relay node may be positioned between a base station (called an eNodeB in the LTE standard) and a user terminal (called user equipment (UE) in the LTE standard) so that transmissions between the base station, referred to herein as the donor base station, and the user terminal are relayed by the relay node. Release 10 of LTE supports Type 1 relay nodes, which appear to the user terminal as a separate base station distinct from the donor base station. The service areas covered by a Type 1 relay nodes, referred to herein as a relay cells, also appear to a user terminal as separate cells distinct from the cells of the donor base station. In the following discussion, references to relay nodes are to Type 1 relay nodes unless otherwise indicated.
The relay cells controlled by the relay nodes have their own Physical Cell ID (as defined in LTE Rel-8) and the relay nodes transmit their own synchronization channels, reference symbols, etc. In the context of single-cell operation, the user terminal receives scheduling information and Hybrid Automatic Repeat-reQuest (HARQ) feedback directly from the relay node and sends control information, such as service requests (SRs), channel quality indications (CQIs) and acknowledgements (ACKs) to the relay node. A Type 1 relay node is backward compatible and appears as a base station to Release 8 user terminals. Thus, from the perspective of a user terminal, there is no difference being served by a base station or a Type 1 relay node.
Transmissions between the relay node and the donor base station are over a radio interface called the Un interface. The Un interface, referred to herein as the backhaul link, provides backhaul transport for data transferred between the relay node and all connected user terminals, and the core network. The radio protocols used on the backhaul link are based on the LTE Rel-10 standard. Transmissions between user terminal and relay node are over a radio interface called the Uu interface. The Uu interface is referred to herein as the access link. The radio protocols for the access link are the same as for direct communication between the user terminal and a base station (e.g., donor base station) without a relay node being located in between.
The relay node comprises two main parts: a user terminal part for communicating with the donor base station over the Un interface and a base station part for communicating with user terminals over the Uu interface. The user terminal part behaves similar to a normal user terminal. Thus, normal user terminal access procedures and methods are employed on the Un interface to establish connections between the relay node and the donor base station. These access procedures are described in 3GPP TR36.806, “Evolved Universal Terrestrial Radio Access (E-UTRA); Relay Architecture for E-UTRA (LTE-Advanced) (Release 9).”
When the relay node attaches to the LTE network, it first re-uses the conventional LTE user terminal attach procedure in order to establish Internet Protocol (IP) connectivity with the core network. Once this attach procedure is completed, the relay node contacts an Operations and Maintenance (O&M) system or other network node in the core network to become active as a base station.
Not all relay nodes are expected to have the same hardware and software configuration. Proposals have been made to indicate to the base station that a device attaching to the network is actually a relay node rather than a user terminal. However, no mechanism currently exists to uniquely identify the relay node to the base station or to provide configuration information for the relay node to the base station. Consequently, the donor base station will typically use a default configuration for communications with all relay nodes, which may not be optimal in all cases.